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The effect of gamma radiation on the quality characteristics o f pomegranate kernels stored in plastic pouches at refrigerator temperatures was studied. Irradiation at doses of 0.2 and 0.4 Mrad markedly reduced the load of potential spoilage microorganisms. Fungal contaminants exhibited much higher radiation resistance than bacterial contaminants, which were eradicated at 0.4 Mrad. The predominant fungus isolated from non-irradiated pomegranate kernels was Penicillium frequentans while after irradiation at all doses tested kernels yielded the fungus Sporofhrix cyanescens. An adverse effect of irradiation on colour was observed. The results of a taste evaluation panel did not indicate a significant difference between irradiated and control samples. lt is concluded that the feasibility of irradiation for prolonging the storage life of packaged pomegranate kernels is questionable.

A hot water dip at 50°C for 2 min was more effective than 1 KGy of gamma radiation in reducing Botrytis cinerea and Rhizopus stolonifer decay in inoculated light-red tomatoes. The combined hot water and radiation treatment acted synergistically on fungal development resulting in 1.7% and 10.0% infection by B. cinerea and R. stolonifer, respectively, after 5 days at 23°C compared with 67% and 100% infection in the non-treated controls. Under natural infection conditions, hot water dip followed by irradiation at 0.5 KGy totally eliminated decay by Alternaria alternata during 8 days at 23°C. All treatments caused more rapid fruit softening, with 20% soft fruit in the combined treated fruit compared with zero soft fruit in the non-treated control.

The effect of gamma irradiation of whole-corn grains on mold development during storage and on nutritional value for broiler chicks was determined in two experiments. Moisture content (MC) of the grains was either ca. 13.5 (natural) or ca. 16% (moistened); irradiation was applied at dosages of 7 and 10 kilogray (kGy) with follow-up of fungal development during the next 80 and 96 days. Feeding tests were initiated after 120 and 173 days of storage in Experiments 1 and 2, respectively. Mold development was observed already after 11 days in moistened grains. Irradiation, particularly of grains with low MC, delayed, but did not prevent fungal development. Fat content of moistened grains at the end of the storage period was not changed in Experiment 1, but it decreased markedly in Experiment 2. Irradiation did not affect this variable. The moistened corn did not adversely affect chick performance in Experiment 1, whereas in Experiment 2 it significantly (P It was concluded that gamma irradiation at the dosages applied was effective in preventing moldiness of low MC corn grains for ca. 60 days. However, moldiness per se did not necessarily disqualify the grains for use in poultry nutrition. Before use, such grains should be analyzed for the presence of mycotoxins, and their fat content determined to ensure their safety and economical value.

The effects of γ-radiation on the immature stages ofLiriomyza trifolii Burgess were studied with doses of 2000-25 Gy. The high doses were lethal to all stages. At doses of 750 Gy or less, larvae survived to pupate, but their number was reduced and the majority were either dead or deformed and did not give rise to adults. Eggs and prepupae were more susceptible to radiation than other stages. Larval radiosensitivity decreased with progressing instar, and pupal sensitivity decreased with increasing age.

Ochratoxin content in sclerotia collected from grains of barley, wheat, and corn inoculated with Aspergillus ochraceus was significantly higher than that accumulated in sclerotia produced on synthetic medium (SM) (95.8, 47.3, 9.2 and 1.75 μg/g sclerotia, respectively). However, when sclerotia harvested from those grains were grown for 14 d on SM the amount of ochratoxin produced by the colonies formed was 3.4, 2.7 and 3.0 μg/plate, as compared with 5.2 μg/plate produced under the same growth conditions by colonies initiated from sclerotia which originated from the SM. Complete mortality of sclerotia from grains or SM occurred at a dose of 200 krad, but none of the levels tested (25, 50 or 100 krad) caused an increase in ochratoxin production. A marked reduction in sclerotial germination was recorded for sclerotia obtained from SM but not for those obtained from wheat grains after exposure to combined treatments of irradiation plus heat. Nevertheless, the combined treatment did not consistently result in significantly different quantities of ochratoxin produced.

APT agar (APT) used for enumeration of lactic acid bacteria and Plate Count agar (PCA) applied for total count were sterilized by gamma radiation using radiation dose of 10–15 kGy. Radiosterilized PCA and APT modified by adding catalase prior to irradiation, or APT with increased content of yeast extract performed, as well as, the heat sterilized commercial media. Growth performance was evaluated on several strains of microorganisms, as well as, by enumeration of bacteria in food products. Radiosterilization of culture media in final packaging, can be applied to produce dip slide kits containing PCA or APT.

Spiegel-Roy P. and Padova R. Radiosensitivity of Shamouti orange (Citrus sinensis) seeds and buds. Radiation Botany 13, 105-110, 1973.-Seeds, budwood and plants of the orange cv. Shamouti were irradiated with a 60Co gamma source. The LD50 for seeds was between 8 and 10 kR, with 12·5 kR being 90 per cent lethal. Peeled seed germinated earlier, but showed no differences in radiosensitivity. Some stimulation of germination rate and early growth with low doses was found, but the effect was inconsistent and in most cases temporary. Buds from shoots originating on plants irradiated with 4–8 kR, did not sprout as well as the control, when budded to rootstocks. Buds from shoots irradiated after being detached from the tree, had a LD50 below 5 kR, with few buds surviving the 7·5 kR dose. No appreciable differences in radiosensitivity between buds of nucellar and ‘old clone’ origin were noted.

Tryptic soy broth/agar, brain heart infusion agar and Columbia broth/agar, all widely used in the bacteriological laboratory, were radiation-sterilized at a dose of 10–15 kGy. The media were tested for the growth of 12 different micro-organisms, including fastidious pathogens such as Streptococcus pyogenes, Strep, pneumonias, Haemophilus influenzas and Neisseria meningitidis. Solid and fluid media supplemented with catalase before irradiation performed well in comparison with heat-sterilized media.